University of Groningen
Measurements with time-of-flight detector for the new HypHI
experiment
Author:
Birthe Stam
Supervisor:
Dr. M Kavatsyuk
July 6, 2017
Abstract
To confirm the existence of a recently seen neutral bound state, the
3
Λn bound state, a new setup has to be made. In this research the time resolution of the Plastic Bowl detector will be determined and if possible improved. There has been found that the time resolution of this detector is not accurate enough to be used as a time-of-flight detector in the new HypHI experiment, but there might be possibilities to use it as a start detector for a drift chamber. The best found time resolution for one detector has a value of 0.386 ± 0.039 ns, while for using this detector as a time-of-flight detector a time resolution of approximately 0.20 ns is required.
Contents
1 Introduction 4
2 Theory 4
2.1 Hypernuclei . . . 4
2.2 3Λn bound state . . . 5
2.3 Detectors . . . 6
3 Experimental Setup 8 3.1 Setup for calibration measurement . . . 8
3.2 Setup for detectors measurement . . . 9
4 Results 12 4.1 Calibration . . . 12
4.1.1 Measurement data . . . 12
4.1.2 Calculations . . . 13
4.2 Detectors . . . 14
4.2.1 Time resolution measurements detectors 64 and 64-2 with setup 4 . . . 14
4.2.2 Measurement with detector part 64-2, panel detector and setup 4 . . . 17
4.2.3 Measurement with detector part 64-2, panel detector and setup 5 . . . 20
4.2.4 Measurement with detector 64-2, dissembled detector 64 and setup 4 . . . 24
4.2.5 Measurement with detector part 598, panel detector and setup 4 . . . 27
4.2.6 Measurement with detector 598, panel detector and setup 5 29 5 Discussion 32 6 Conclusion 32 6.1 Detectors 64 and 64-2 . . . 32
6.2 Detector 598 . . . 33
6.3 Final conclusion . . . 33
7 Acknowledgements 34
1 Introduction
In the HypHI phase 0 experiment three types of particles have been observed, including two hypernuclei (3ΛH and 4ΛH). Besides these particles a neutral nuclear bound state with two neutrons and a Λ-hyperon, 3Λn has been observed [1].
While until now there is predicted that the only neutral bound system exists in neutron stars. To confirm the existence of this particle and to explore it further, a new experiment and setup has to be made. One of the components of the new set-up will be a time-of-flight (TOF) detector for charged particles. The aim of this bachelor research is to test an old previously used detector named
”Plastic Bowl” and characterize time resolution of this detector, with different setups and approaches. One detector will be dissembled and if possible improved.
The required time resolution to use this detector as a TOF-start detector is around 0.20 ns and for a TOF-stop detector even smaller than 0.20 ns [7]. Finally there has to be concluded whether this detector can be employed in the new HypHI experiment.
2 Theory
2.1 Hypernuclei
A hypernuclei is a nucleus in which one up- or downquark has been replaced by a strange quark [2]. They have been discovered by Marian Danysz and Jerzy Pniewski in 1952 [8]. The lightest baryon which involves at least one strange quark, called a hyperon, is the Λ-hyperon and has a measured lifetime of
263.2 ± 2 ps [9]. To study nucleon-Λ interactions, Λ-hypernuclei are studied in- stead, due to the lifetime of hyperons. Namely, the small lifetime of the Λ-hyperons result in a too short flight path to separate the interactions properly [4].
A new experiment, with the aim to demonstrate the feasibility of hypernuclear spectroscopy with heavy ion beams, has been carried out by HypHI Collaboration.
The invariant mass method was used to perform the spectroscopy of hypernuclear products of 6Li projectiles on a carbon target at 2 A GeV. Invariant mass dis- tributions were found for p + π−, 3He + π− and 4He + π−. In these invariant
mass spectra peaks were seen with corresponding significances of 6.7σ, 4.7σ and 4.9σ. Their lifetimes were deduced by first reconstructing the invariant mass, then situating the longitudinal position and finally extracting the lifetimes by using an unbinned maximum likelihood fitting method. These values were measured to be 262+56−43± 45 ps for Λ, 183+42−32± 37 ps for 3ΛH and 140+48−33± 35 ps for4ΛH [5].
2.2
3Λn bound state
During this HypHI Phase 0 experiment, possibly a neutral nuclear bound state with two neutrons and a Λ-hyperon has been observed. Besides for the decays mentioned before, the invariant mass distributions of d + π−and t + π− were stud- ied as well. Two points had to be investigated to be able to interpret the results from the signals obtained. Firstly, it was demonstrated that the analysis method did not create signals by itself and secondly it has been checked that multi-body decays of other hypernuclei cannot induce such signals. So there was concluded that a possible interpretation of these observed signals could be the two- and three- body decays of this 3Λn bound state [1].
The existence of the 3Λn bound state can provide information on the three-body force, which could help to understand the lifetime time of the hypertritions better.
Also, until now all known nuclei are a positively charged bound systems consisting of nucleons (neutrons and protons). It is predicted that a neutron star exists of a neutral bound state as well. Conformation of the existence of 3Λn could lead to more information on neutrons stars. This is why the existence of the 3Λn has to be confirmed and a new setup has to be made.
The setup proposed by the HypHI collaboration would be a combination of the HypHI experiment and FRS [12]. The proposed setup can be found in figure 1.
The 6Li-beams come from the first half of FRS and are coming from the left side of the figure. The beams pass trough the START-counter of the TOF measure- ment and is then impinged on the Target. Behind the decay volume there are several tracking counters, for which the HypHI scintillation fiber detectors and drift chamber are considered to be used. After this part there is a dipole magnet.
The possible candidate for this magnet is now at J-PARC in Japan, but not in use
and available, and the shipping is arranged. For the upward bending particles (π−) there are two detectors to measure them, namely DC and TOF-plus detectors. For the other particles (deuterons), a second magnet will be placed behind the first magnet, to compensate for the bending in the first magnet. At the exit of the S2 area, the second half of FRS is placed which analyses the particles [1].
Figure 1: Proposed setup at S2 os FRS with a second dipole magnet [1]
2.3 Detectors
As mentioned in section 2.2, one part of this new setup would include a TOF- detector. There is a possible candidate which could be used in the new HypHI setup, but this one needs to be tested and optimized. The detecting principle of a TOF-detector is based on the time of flight between two scintillators. With this difference in time and a known velocity and bending radius, it is possible to distinguish between lighter and heavier particles. The time-of-flight difference for two particles with masses m1 and m2 and energies E1 and E2 is given by:
∆t = 2pLc2(m21− m22) [A]
with L the distance between to start and stop scintillators and p the momentum [6].
The time resolution of one detector can be calculated with the following formula:
σtot2 = σ21+ σ22 [B]
with σ1 and σ2 the time resolution of the two separate detectors and σtot the σ from the time difference measurement. This σ can be extracted from the time-
difference histograms obtained in this experiment.
The detector which will be tested is hourglass shaped and exists of two equal but reversed parts as can be seen in figure 4. Each part exists of 6 equal detectors, which all exist of among others of a photo-multiplier and organic plastic scintilla- tion material. The photo-multiplier and the plastic scintillator are connected by a connecting material. In total there thus 12 detectors inside the ”Plastic Bowl”, which can be tested separately or combined. A dissembled detector can be seen in figures 2 and 3. Detectors number 64, 64-2 and 598 have been tested.
Figure 2: Photo-multiplier and protecting shield
Figure 3: Scintillation material visible after re- moving photo-multiplier The desired property of this research, the time resolution, is affected by different factors. First of all time, the time resolution depends on the type of scintillation material used in a detector. The shorter the decay time of the scintillation material, the faster signals can be obtained and good time information can be provided [10].
Also, the choice of photo multiplier has an influence, the longer the distance to the anodes the longer that takes and thus the whole process takes [10]. Finally, the time resolution depends on the shape and size of the whole detector. Since the longer the path the particle and/or photon has to travel, the longer it takes.
All of these factors determine how fast an incoming particle results in a signal and thus influences the time resolution of a detector.
3 Experimental Setup
3.1 Setup for calibration measurement
Figure 4: Setup for the time difference calibration measurement.
The setup for the calibration measurement was built as described here and can be seen in figure 4. Signals from detector 1 (D1) and detector 2 (D2) are splitted with a 50Ω splitter (split) and are then read by a Constant Fraction Discriminator (CFD) and a Sampling Analogue to Digital Converter (SADC) . After that, the signals from te CFD are delayed with a Delay Generator (delay) and coincidence signals are selected with a Coincidence Quad (coincidence). Signals from the delay and coincidence devices are then converted by an ECL/NIM/ECL Converter (con- verter). The Data Acquisition device (DAQ) collects the signals coming from the SADC and coincidence devices. At last, signals from the converter are collected by the DAQ.
The read-out of the data is done by a computer. Data have been analyzed in the data analysis Framework ROOT. [11] Energy measurement data is obtained by the SADC, a Flash Analogue to Digital Converter. With the program his- tograms of the energy of the (in this case) two detectors can be made. To extract energy information from the data, the program written in CC+ is used to integrate
over peaks deviating from the baseline. From the resulting energy histograms the values for the so-called cuts can be extracted by looking at intervals most likely corresponding to signals of particles which travelled all their way through the de- tector. The SADC consists of a series of comparators, which compares the input voltage to different unique reference voltages. For this type of ADC, the compara- tors are the sampling devices. The output of the comparators are connected to a priority encoder circuit, which results in a binary output.
Also histograms for the difference in time between the signals of the two detectors are made with the data selected by the manually inserted values for the cuts. From these histograms the σ can be extracted which corresponds (according to formula [B]) to the time resolution of the detector, which is the desired property for this research.
The cuts are made to select only the events of interest from all the data. One reason for these cuts is that only signals which correspond to particles who trav- elled all their way through the detector and not just partially are useful. From the peaks in the energy spectra it can be extracted which values should be taken for the cuts, since these peaks correspond to particles with the highest energy deposition and thus longest distance travelled. Also, the threshold for the signals should be low enough, since we want to detect the first photon which arrives. If the threshold is too high and not equal during all the measurements, it is hard say whether the changes in the setup and detector have got an influence or if the data changed due to the change in threshold.
3.2 Setup for detectors measurement
The setup for the first detectors measurement is the same as above for the calibra- tion measurement, only with a different D1 and D2, namely the panel detectors are replaced by detectors of the TOF-detector. The setup can be found in fig- ure 4. The read-out and conversion of the data also works the same as for the calibration measurement. For the first measurements, the detector which had to be tested was hourglass shaped as can be seen in figure 6. For the second round of measurements, the upper part of the detector was removed and one of the for the calibration measurement used panel detectors was placed instead.
For an other round of measurements, the setup was adapted. An extra delay device (delay 2) and amplifier (amp) device were added, the setup can be found in figure 5. The detector itself was setup as in figure 7, with a panel detector on top of the pyramid shaped detector. The amplifier was added to increase the change that the first photon arriving at the photomultiplier results in a signal, which would result in a lower time resolution.
Different setups and measurements were taken to look for limiting factors for cre- ating a lower time resolution. Limiting factors for the time resolution of this de- tector could among others be related to the scintillation material, choice of photo- multiplier or size and shape of the detector. As was explained in section 2.3. That is why for some of the measurements the original geometry of the TOF-detector was changed into the geometry of figure 7. This results in the following list of measurements taken:
• Measurement with setup as in figure 3 and detectors 64 and 64-2
• Measurement with setup as in figure 3, a panel detector and detector 64-2
• Measurement with setup as in figure 6, panel detector and detector 64-2
• Measurement with setup as in figure 3, dissembled detector 64 and detector 64-2
• Measurement with setup as in figure 3, panel detector and detector 598
• Measurement with setup as in figure 6, panel detector and detector 598
Figure 5: Setup for the detector measurements with added amplifier and delay device
Figure 6: Detector hourglass shaped
Figure 7: Detector pyramid shaped with panel detector
4 Results
4.1 Calibration
First a calibration measurement was done to be able to convert the unit channels into the unit nanoseconds. Measurements were done with two panel detectors, one measurement with these two detectors placed on top of each other and one with a vertical distance of s = 1.155 ± 0.005 m in between them. The time it takes for a particle which travels with the speed of light to travel this distance has been calculated. This time difference corresponds to the mean channel difference for both measurements, and the the further conversion calculations can be found in the section calculations.
4.1.1 Measurement data
Figure 8: Graph for the timedifference measurement with detectors on top of each other.
Figure 9: Graph for the timedifference measurement with detectors separated on top of each other.
4.1.2 Calculations
The time difference will be measured according to the formula s = v ∗ t with v = c = 229792458m/s−1[3] and the distance is measured to be
s = 1.155 ± 0.005 m. This gives t = s/v = 3.853 ± 0.02 ns. The error in the time difference is calculated as following: (∆(t)/t)2 = (∆(s)/s)2 + (∆(v)/v)2. The time difference can be extracted from figure 8 and 9, and is stated to be
∆channels = 113.2 ± 0.2 − 6.395 ± 0.441 = 106.8 ± 0.5 channels. Which gives a calibration of t/channels = 3.853 ± 0.02/106.8 ± 0.5. So this gives a time interval of 3.6 ∗ 10−2± 0.0003 ns per channel, with the error calculated in the same way as was done above.
The time resolution of the panel detectors can be extracted from graph 8 and graph 9 as well. The σ for graph 8 is given as 12.42 ± 0.20 channels, which gives a σ of 0.447 ± 0.008 ns. With formula [2]: σ2tot = σ12+ σ22 the time resolution for one detector can be calculated. Since σ1 is equal to σ2, the time resolution for one detector will be equal to: σ√tot
2. For a single panel detector, this results in a value of 0.447±0.008√
2 = 0.316 ± 0.006 ns.
4.2 Detectors
4.2.1 Time resolution measurements detectors 64 and 64-2 with setup 4
The data for the first experiment with the hourglass shaped detectors 64 and 64-2, as can be seen in figure 10, does not correspond to the required time resolution of approximately 200 ns. There could be at least two reasons for this, firstly the threshold for the energy was too low. Secondly the geometry of the setup was not optimal, because of the hourglass shape of the detector the energy deposit was not high enough and thus resulted in an insufficient time difference sigma of 0.8161 ± 0.0412 ns (figure 10). This sigma leads to a time resolution of
σ1 = 0.386 ± 0.039 ns for the upper detector 64. This is calculated with formula [B] and σ2 = 0.719 ± 0.013 ns and σtot = 0.8161 ± 0.0412 ns. The value for σ2 is calculated as described in the next paragraph 4.2.2. In figures 11 and 12 the energy spectra and 2D energy plot, the other time difference figures and the table with the values for the different cuts can be found.
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Figure 10: Hourglass shaped detectors 64 and 64-2 measurement.
Cut values
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values energy 2 cut
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Figure 11: Energy spectra and 2D energy plot
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Figure 12: Measurements with detectors 64 and 64-2 and setup 4 cut 1, 3 and 4
4.2.2 Measurement with detector part 64-2, panel detector and setup 4 That is why for the second measurement, the setup was changed into a panel de- tector on top of pyramid shaped detector. The data for this measurement was also analyzed with different so-called cuts, since not all of the histogram data was useful. The best time resolution of part 64-2 was found for cut 3 with a value of 0.719 ± 0.013 ns. Time resolution was calculated with formula [B] and a value of 0.316 ± 0.006 ns for σ1 as calculated before. For σtot a value of
0.7855 ± 0.0143 ns was used, which can be found in figure 13.
h_dTime_cut
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h_dTime_cut
Figure 13: Best time resolution for measurements with the detector part 64-2 and a panel detector.
All the other data and different cuts can be found in figure 15. These different cuts were made to select only the data which corresponds to particles which travel their way totally through the detector and not just partially. The values for the different cuts were determined by looking at the energy spectra of both detectors 64-2 and the panel detector. The energy spectra and 2D energy plot can be found in figure 14.
Cut values
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Figure 14: Energy spectra and 2D energy plot
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Figure 15: Measurement panel detector on top of detector 64-2 with cuts 0, 1 and 2
4.2.3 Measurement with detector part 64-2, panel detector and setup 5 Since the time resolution was not as accurate as needed yet, an amplifier and ex- tra delay device were added. The extra delay device had to be added to delay the trigger since the amplifier causes an extra delay. The amplifier is added to get a bigger chance of detecting the first photon that arrives. Unfortunately this did not result in a better time resolution for detector part 64-2. Results can be found in figures 18 and 19. The best found value for the resolution of the two detectors combined was σtot = 0.8427 ± 0.0209 ns, see figure 16. This results in a time resolution of σ1 = 0.781 ± 0.02 ns for detector 64-2, with formula [B] and σ2 = 0.316 ± 0.006 ns for the panel detector.
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Constant 26.92 ± 0.93 Mean −41.4 ± 0.0 Sigma 0.8427 ± 0.0209
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Figure 16: Best time resolution for measurements with the detector 64-2 and a panel detector with setup 5
Cut values
Cut values energy 1
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Figure 17: Energy spectra and 2D energy plot
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Figure 18: Measurement panel detector on top of pyramid shaped detector 64-2 with amplifier and cut 0, 1, 2 and 3
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/ ndf
χ2 249.7 / 206
Constant 37.13 ± 1.05 Mean −41.44 ± 0.02 Sigma 0.8584 ± 0.0166
Time (ns)
−60 −40 −20 0 20 40 60
Counts
0 10 20 30 40 50
h_dTime_cut
Entries 2525
Mean −1177
RMS 65.13
/ ndf
χ2 249.7 / 206
Constant 37.13 ± 1.05 Mean −41.44 ± 0.02 Sigma 0.8584 ± 0.0166
h_dTime_cut
h_dTime_cut
Entries 1683
Mean −1173
RMS 45.76
/ ndf
χ2 224.8 / 190
Constant 23.58 ± 0.85 Mean −41.3 ± 0.0 Sigma 0.8668 ± 0.0220
Time (ns)
−60 −40 −20 0 20 40 60
Counts
0 5 10 15 20 25 30 35 40
h_dTime_cut
Entries 1683
Mean −1173
RMS 45.76
/ ndf
χ2 224.8 / 190
Constant 23.58 ± 0.85 Mean −41.3 ± 0.0 Sigma 0.8668 ± 0.0220
h_dTime_cut
h_dTime_cut
Entries 1529
Mean −1170
RMS 85.77
/ ndf
χ2 176.8 / 166
Constant 21.12 ± 0.81 Mean −41.15 ± 0.03 Sigma 0.9068 ± 0.0263
Time (ns)
−60 −40 −20 0 20 40 60
Counts
0 5 10 15 20 25 30 35
h_dTime_cut
Entries 1529
Mean −1170
RMS 85.77
/ ndf
χ2 176.8 / 166
Constant 21.12 ± 0.81 Mean −41.15 ± 0.03 Sigma 0.9068 ± 0.0263
h_dTime_cut
h_dTime_cut
Entries 1535
Mean −1166
RMS 66.38
/ ndf
χ2 158.6 / 166
Constant 21.33 ± 0.77 Mean −40.96 ± 0.03 Sigma 0.9163 ± 0.0238
Time (ns)
−60 −40 −20 0 20 40 60
Counts
0 5 10 15 20 25 30
h_dTime_cut
Entries 1535
Mean −1166
RMS 66.38
/ ndf
χ2 158.6 / 166
Constant 21.33 ± 0.77 Mean −40.96 ± 0.03 Sigma 0.9163 ± 0.0238
h_dTime_cut
h_dTime_cut
Entries 828
Mean −1165
RMS 34.14
/ ndf
χ2 122.5 / 141
Constant 10.92 ± 0.56 Mean −40.82 ± 0.04 Sigma 0.9326 ± 0.0375
Time (ns)
−60 −40 −20 0 20 40 60
Counts
0 2 4 6 8 10 12 14 16 18
h_dTime_cut
Entries 828
Mean −1165
RMS 34.14
/ ndf
χ2 122.5 / 141
Constant 10.92 ± 0.56 Mean −40.82 ± 0.04 Sigma 0.9326 ± 0.0375
h_dTime_cut
Figure 19: Measurement panel detector on top of pyramid shaped detector 64-2 with amplifier and cut 4, 6, 7, 8 and 9
4.2.4 Measurement with detector 64-2, dissembled detector 64 and setup 4
h_dTime_cut
Entries 544
Mean −11.12
RMS 0.7299
/ ndf
χ2 92.6 / 98
Constant 9.332 ± 0.627 Mean −11.2 ± 0.0 Sigma 0.698 ± 0.039
Time (ns)
−30 −25 −20 −15 −10 −5 0 5
Counts
0 2 4 6 8 10 12 14 16 18 20
h_dTime_cut
Entries 544
Mean −11.12
RMS 0.7299
/ ndf
χ2 92.6 / 98
Constant 9.332 ± 0.627 Mean −11.2 ± 0.0 Sigma 0.698 ± 0.039
h_dTime_cut
Figure 20: Best time resolution for measurements with the dissembled detector part 64 and part 64-2.
Finally, detector 64 was dissembled and the connecting material between the photo-multiplier and the scintillation material was renewed. A new measurement was done just as before for the hourglass shaped detector setup before, to check whether this connecting material was not working properly anymore. For this measurement a value of 0.698 ± 0.039 ns was found for the σ of the time difference measurement, see figure 20 This leads with σ1 = 0.719 ± 0.013 ns to a negative value for the time resolution σ2, which does not exist. The threshold does was lower for this measurement than the measurements before. The other graphs and cuts can be found in figure 21 and 22.
Cut values
Cut values energy 1
cut
values energy 2 cut
1 2000-5000 6000-14000
2 2000-5000 7000-13000
3 3800-5100 7000-13000
4 3800-5100 8000-12000
5 3800-5100 9000-11000
6 4000-5300 8000-12000
h_Energy_1
Entries 15197 Mean 3897 RMS 2826
Chanels
0 10 20 30 40 50 60 70 80 90 100
103
×
Counts
0 100 200 300 400 500
h_Energy_1
Entries 15197 Mean 3897 RMS 2826
h_Energy_1
h_Energy_2
Entries 15197 Mean 6878 RMS 5037
Chanels
0 10 20 30 40 50 60 70 80 90 100
103
×
Counts
0 50 100 150 200 250 300
h_Energy_2
Entries 15197 Mean 6878 RMS 5037
h_Energy_2
Chanels 0 5000 10000 15000 20000 25000 30000 35000 40000 45000
Chanels
0 5000 10000 15000 20000 25000 30000 35000 40000 45000
50000 h_E1_E2
Entries 15543 Mean x 3869 Mean y 6822 RMS x 2557 RMS y 4662 h_E1_E2 Entries 15543 Mean x 3869 Mean y 6822 RMS x 2557 RMS y 4662 h_E1_E2
Figure 21: Energy spectra and 2D energy plot
h_dTime_cut
Entries 3192
Mean −343.2
RMS 38.77
/ ndf
χ2 209.4 / 206
Constant 31.26 ± 0.73 Mean −12.01 ± 0.03 Sigma 1.346 ± 0.021
Time (ns)
−60 −40 −20 0 20 40 60
Counts
0 5 10 15 20 25 30 35 40 45
h_dTime_cut
Entries 3192
Mean −343.2
RMS 38.77
/ ndf
χ2 209.4 / 206
Constant 31.26 ± 0.73 Mean −12.01 ± 0.03 Sigma 1.346 ± 0.021
h_dTime_cut
h_dTime_cut
Entries 2404
Mean −346.6
RMS 36.73
/ ndf
χ2 214 / 194
Constant 24.64 ± 0.68 Mean −12.11 ± 0.03 Sigma 1.253 ± 0.023
Time (ns)
−60 −40 −20 0 20 40 60
Counts
0 5 10 15 20 25 30 35
h_dTime_cut
Entries 2404
Mean −346.6
RMS 36.73
/ ndf
χ2 214 / 194
Constant 24.64 ± 0.68 Mean −12.11 ± 0.03 Sigma 1.253 ± 0.023
h_dTime_cut
h_dTime_cut
Entries 851
Mean −317.3
RMS 23.51
/ ndf
χ2 118.4 / 118
Constant 13.18 ± 0.68 Mean −11.14 ± 0.03 Sigma 0.7862 ± 0.0304
Time (ns)
−60 −40 −20 0 20 40 60
Counts
0 5 10 15 20 25
h_dTime_cut
Entries 851
Mean −317.3
RMS 23.51
/ ndf
χ2 118.4 / 118
Constant 13.18 ± 0.68 Mean −11.14 ± 0.03 Sigma 0.7862 ± 0.0304
h_dTime_cut
h_dTime_cut
Entries 292
Mean −317.5
RMS 20.54
/ ndf
χ2 79.57 / 84
Constant 4.078 ± 0.444 Mean −11.18 ± 0.07 Sigma 0.8267 ± 0.1033
Time (ns)
−60 −40 −20 0 20 40 60
Counts
0 2 4 6 8 10 12 14
h_dTime_cut
Entries 292
Mean −317.5
RMS 20.54
/ ndf
χ2 79.57 / 84
Constant 4.078 ± 0.444 Mean −11.18 ± 0.07 Sigma 0.8267 ± 0.1033
h_dTime_cut
h_dTime_cut
Entries 411
Mean −317.6
RMS 20.79
/ ndf
χ2 82.68 / 93
Constant 6.517 ± 0.537 Mean −11.14 ± 0.05 Sigma 0.7425 ± 0.0559
Time (ns)
−60 −40 −20 0 20 40 60
Counts
0 2 4 6 8 10 12 14 16
h_dTime_cut
Entries 411
Mean −317.6
RMS 20.79
/ ndf
χ2 82.68 / 93
Constant 6.517 ± 0.537 Mean −11.14 ± 0.05 Sigma 0.7425 ± 0.0559
h_dTime_cut
Figure 22: Measurement dissembled detector 64 and 64-2 with cuts 1, 2, 3, 5 and 6
4.2.5 Measurement with detector part 598, panel detector and setup 4 The same measurement with a panel detector on top of, in this case detector 598, was done. The result can be seen in figure 23, a value of 1.921 ± 0.021 ns was found for the time resolution. Calculated with formula [B] and for σ2 the time resolution of the panel detector 0.316 ± 0.006 ns.
h_dTime_cut
Entries 8857
Mean −10.5
RMS 2.205
/ ndf
χ2 1336 / 364
Constant 54.27 ± 0.86 Mean −10.48 ± 0.03 Sigma 1.947 ± 0.022
Time (ns)
−40 −30 −20 −10 0 10 20
Counts
0 10 20 30 40 50 60 70
80 h_dTime_cut
Entries 8857
Mean −10.5
RMS 2.205
/ ndf
χ2 1336 / 364
Constant 54.27 ± 0.86 Mean −10.48 ± 0.03 Sigma 1.947 ± 0.022
h_dTime_cut
Figure 23: Data for measurement with panel detector op top of detector 598
